(1) Field of the Invention
This invention relates to a cable sectional assembly which houses a series of concatenated electronic modules, and which allows for the assembly to flex without damaging the connections between the electronic modules and the wires, microwave signal coaxial cables or other forms of electrical hook-up media connecting the modules, and which has strong backbone and integral strength while nevertheless being sufficiently flexible for high flexture applcations.
(2) Description of the Prior Art
Notwithstanding the term xe2x80x9cPrior Artxe2x80x9d being used in the caption of this subsection, and as a legend in connection with FIG. 1, it is to be understood that the term is not intended to mean or imply that the inventors admit that any technology characterized as an unsuccessful attempt, or that the apparatus depicted in FIG. 1, constitutes a 35 USC xc2xa7102 anticipation of the present invention.
Naval submarines are provided with radio reception while submerged through the facility of a buoyant cable antenna (BCA) system which consists of a multisectional cable which trails behind the submarine. A predetermined trailing portion of the multisectional cable is buoyant and floats on the surface, including the trailingmost section which is a cable section housing a single-conductor antenna element. As an improvement of the BCA system, a new capability was conceived of inserting a section of the cable line immediately inboard of the single-conductor antenna element section which houses a series of electronically concatenated electronic circuit modules. These modules provide radio electronics functions which enhance and/or augment the BCA system""s radio electromagnetic wave pickup capablility.
Prior to the present invention the sections of the BCA line were of a form of construction having the core structure of the cable surrounded by a layer of polyethylene applied as a molten extrusion. However, because polyethylene requires high heat during the extrusion process, it was dismissed as a molding material for fear that electronics molded therein would be damaged by the extreme heat. Accordingly, a room temperature curing compound, namely polyurethane, was looked to for the molding compound.
U.S. Pat. No. 5,606,329 to Ramotowski et al, entitled xe2x80x9cBuoyant Cable Antennaxe2x80x9d, discloses a form of construction of a cable sectional assembly in which a radio electronics package is surrounded by a cured polyurethane and microballon composition.
One prior approach employed in an attempt to devise an operationally satisfactory cable sectional assembly for housing concatenated electronic modules employed hard polyurethane encapsulant being locally distributed around the circuit modules, with a softer an overmolding of a mixture of polyurethane and buoyant particulates distributed between the modules and around the hook-up media, as shown in the prior art FIGS. 1 and 1A. In this construction the polyurethane and buoyant particulate mixture was molded into direct contact with the items of hook-up media between modules. This approach was abandoned because it was found that assemblies fabricated in this way exhibit a plurality of problems which are basically related to the flexing of the wires, microwave coaxial cables, or other forms of electrical hook-up media potted within the mixture.
More specifically, during testing of a construction of cable sectional assembly fabricated in accordance with this prior approach to devise the assembly, problems arose as the cable was flexed around a 12-inch diameter mandrel which simulated the intended operational environment in which the assembly would be deployed and retrieved by a 12-inch power capstan. The continuity of the electronic modules and their hook-up media became intermittent, eventually forming an open circuit. It was discovered that the flexing of the cable sectional assembly had caused the connections of the hook-up media with the electronic modules to fracture at the soldered joints which formed the electrical coupling connection at the juncture between each end of a hook-up medium and a terminal of the adjacent electronic module. As may be seen in FIG. 1A, the hard polyurethane encapsulant and the molding of a mixture of polyurethane and buoyant particulates hold the electrical hook-up media in fixed relationship to the electronic modules as the cable sectional assembly is flexed. The junctures between the ends of the hook-up media and the terminals of the modules become stressed, causing fractures of the soldered connections along the length of the assembly.
While the following patents do include cable designs directed for underwater use as well as cable antennas, none of these patented constructions solve the defects discussed above.
U.S. Pat. No. 1,557,049 to Hammond, Jr. discloses a buoyant electrical antenna. The electrical antenna of Hammond includes an assembly which uses a rigid tubular member extending from an underwater device to the water surface. A single conductor running through the center of the rigid member is used which then extends into a flexible casing having a cylindrical shape with a cavity for encasing the single conductor. Insulating standoffs are used to maintain proper spacing of the single conductor relative to the outside wall of the cylindrical flexible member. The single conductor is insulated and obtains its buoyancy through the use of the flexible cylindrical member being filled with air.
U.S. Pat. No. 4,011,540 to Farr discloses a combined electret hydrophone and transmission line which comprises a plurality of coaxial cable segments coupled by electronic circuit modules, wherein the coaxial cable segments serve as seismic detectors, signal transmission, lines and power supply lines. The coaxial cables of Farr use polytetrafluoroethylene (xe2x80x9cPTFExe2x80x9d) as an integral part thereof for the dielectric material between two conductors. Accordingly, the PTFE used is a part of the coaxial cable provided in Farr, but there is no cavity in which a coaxial cable can loosely fit and independently flex so as to avoid high stress occurring at points of Farr""s coaxial cables"" connections with the electronic circuit modules. Therefore, it is probable that in high flexibility applications, the cable of Farr would not maintain constant transmission capabilities since high stress points would develop and would thereby cut off transmission where the stress points lead to joint fracture. Further, the PTFE layer used in Farr is not firmly bonded at its outer surface to the remaining layer of the coaxial cable thereby causing a weaker assembly to be formed. Still further, Farr""s cable assembly is constructed to have a neutral buoyancy, not a positive buoyancy.
U.S. Pat. No. 4,183,010 to Miller discloses a pressure compensating coaxial line hydrophone and method for detecting mechanical vibrations. The coaxial line includes a coaxial electric cable transducer which includes a combination of an electret with a polymer material having piezoelectric properties. The electret and polymer material are separate flexible materials radially stacked within the cable and preferably constitute a single material formed to have both electret and piezoelectric properties. One polymer which is useful as the piezoelectric material is polyvinylidene fluoride. Similar to Farr, Miller uses PTFE as a dielectric layer between two conductors and not as a protective cable conduit internal to a buoyant cable. In addition, the outer surface of the PTFE layer of Miller""s invention is not etched so as to securely bond with surrounding materials. Again, Miller suffers from the defect in Farr in that flexing of the cable could lead to the formation of high stress points at the connection of the cables with electronic equipment. As a result, it appears that intermittencies in proper functioning of the coaxial line hydrophone would occur if the line were to be used in an operational environment involving severe flexing.
U.S. Pat. No. 4,336,537 to Strickland discloses a bi-directional underwater communication system. The system provides a submerged operator with the capability to communicate with a surface site. A face-mask-mounted microphone and an earphone are connected to a submerged, watertight radio. The radio antenna is carried by a buoy to the surface of the body of water in which the operator is submerged. While Strickland uses a cable assembly, it does not specify any special construction thereof. Accordingly, it is believed that the cable between the surface and the underwater vehicle will be a standard coaxial cable, with no special design modifications and which does not integrate any electronics therein. In addition, Strickland does not disclose the use of a conduit in which the cable is encased and which conduit is surrounded by a buoyant material. In fact, the patent to Strickland does not disclose the use of any protecting tubing for protecting the coaxial cable in any form.
U.S. Pat. No. 4,634,804 to Spalding discloses a streamer cable with protective sheaths for a conductor bundle. A fish-net plastic sheath having oppositely layered, generally parallel plastic filaments is used to cover a conductor wire bundle at points where it could otherwise rub against wire rope strain members of the cable. The filaments are joined at all crossing points to provide an expansible and contractible generally tubular construction that can be readily fitted over the cable bundle during assembly. The sheaths prevent the wire rope strain cables in the streamer section from rubbing directly against the conductor wires and causing interruptions in the insulation and shorts. An unspecified plastic wire mesh is used over the wire bundle to prevent the wire rope strain cables from moving directly on the cable wires. The mesh is expandable and constricts around the wire bundle when in place. Accordingly, free movement of the cables is not allowed since the mesh constricts the cables which may cause the formation of high stress points, and thus fracture.
U.S. Pat. No. 4,694,436 to Gelfand discloses a noise-attenuating streamer-cable bulkhead for use in an oil filled seismic cable assembly. The bulkheads reduce internal acoustic noise in the cable assembly by using baffles. Each bulkhead consists of an annular body with conical surfaces converging at a desired angle, extending outwardly from both ends of the annular body. An axial hole and a plurality of off-axial holes extending through the bulkhead are provided for receiving therethrough, electrical conductors and stress members, respectively. Noise traveling within the tube in a waveguide mode, impinges upon the conical surfaces of the cascaded bulkheads, and is reflected out of the streamer-cable jacket. In Gelfand, no electronic circuit boards or other forms of electronic modules are used, and due to the bulkheads the electrical conductor bundle are not free to move in the plastic jacket, thereby creating potentially damaging stress points.
There exists a need, therefore, for a cable sectional assembly of the type having a function of housing electronic modules, and which allows for the hook-up media interconnecting the modules to be flexible independent of the flexing of the remaining portions of the sectional assembly so as to prevent high stress points and resulting fractures of the electrical coupling connections and the junctures between the ends of the hook-up media and the electronic modules.
The primary object of this invention is to provide a cable sectional assembly of the type which houses a series of electrically concatenated electronic circuit modules, which has improved breakage protection for wires, microwave coaxial cables or other forms of electrical hook-up media interconnecting the modules.
Another object of this invention is to provide a cable sectional assembly of the type housing electronic modules as aforesaid which further has protective oversized conduits for enclosing said hook-up media for allowing flexibility of the hook-up media without damaging connections.
Still another object of this invention is to provide a cable sectional assembly of the type housing electronic modules and having conduits which enclose hook-up media as aforesaid, wherein there is further provided secure bonding between the conduits and the rest of the assembly.
A yet another object of this invention is to provide a cable sectional assembly of the type housing electronic modules and having conduits which enclose hook-up media as aforesaid, whose construction and arrangement endows the assembly with a high degree of backbone strength.
A yet another object of this invention is to provide a cable sectional assembly of the type housing electronic modules and having conduits which enclose hook-up media as aforesaid, which further is bodified by a construction and arrangement of composite molded encapsulations which endow the assembly with sound integral strength while nevertheless being sufficiently flexible for high flexing applications.
Yet further objectives of this invention are to obtain each of the foregoing objectives, with each respective one of the foregoing objectives achieved in a way that makes the assembly buoyant.
The foregoing objects and following advantages are achieved by the provision of a cable sectional assembly housing a series of electrically concatenated electronic modules which have electrical hook-up media interspersed therebetween. In the illustrative embodiment presently proffered, the electronic modules, or electronic structures, housed in the assembly are provided in the form of electronic circuit board assemblies which are sized to be contained within the diametric dimensional envelope of the cable (which is a diameter of approximately 0.65 inches). The hook-up media generally comprises a mix of insulated conductor wires and microwave coaxial cable lines. Each interspersed hook-up media is housed in a flexible tubular member, with the end portions of each individual run of a medium projecting out of the end of the tubular member""s bore. Each end of each medium is joined to a terminal of the adjacent electronic module by means of a connection which provides reliable electrical coupling, such as a soldered connection. The tubular elements are oversized allowing flexibility of the hook-up media (i.e., a bundle of wires and microwave coaxial cables) without damaging connections. Each electronic module is potted in a hard local encapsulation, which forms a unitary encapsulation that further encapsulates the soldered electrical coupling connections at the junctures between each end of a hook-up medium and a circuit board terminal. The hard encapsulation further extends to and forms a moldingly bonded joint with the marginal end portions of the outer surfaces at the adjacent ends of the adjacent tubular elements. Softer more flexible overmolded annular encapsulations fill the annular spaces around the midportion of each tubular element between where the hard encapsulations are bonded to the tubular member""s marginal end portions. A protective outer jacket, or sheath is fitted over the encapsulations. Freedom of movement of the hook-up media within the tubular members is enhanced by choice of the tubing to be made of a flouropolymer material, such as PTFE (sold under the brand name TEFLON(copyright)), and also by coating each individual electrical hook-up medium with such flouropolymer material.
The details of the present invention are set out in the following description and drawings wherein like reference numerals depict like elements.